1. Field of the Invention:
This invention relates generally to multiple speed transmissions using countershafts which are housed within the rear hub of chain driven bicycles coupled with a modification of a conventional bicycle frame which permits the chain to be fully enclosed.
2. Description of the Prior Art:
Multiple speed bicycles commonly use either a chain and derailleur system or a chain driven rear hub employing one or more epicyclic gear trains. Conventional mountain bicycles and all-terrain bicycles (ATBs) use chain and derailleur systems commonly with eighteen speeds, of which about fourteen speeds are useable. On all chain driven bicycles the chain must be kept reasonably clean and well oiled for efficient operation and to prevent premature chain failure and chain maintenance becomes particularly troublesome if the bicycle is ridden extensively on dirt roads and trails. With the current popularity of mountain bicycles, a sealed chain drive is needed to minimize the maintenance problem in a bicycle which can serve for commuting as well as off-road recreation riding. An object of the present invention is to provide a chain enclosure which essentially eliminates chain maintenance coupled with a multiple speed transmission housed within a sealed gear case inside the rear wheel hub, with a range of gear ratios comparable to the currently popular mountain bicycles using the chain/derailleur system.